Boiler feed system



Dec. 17, 1940.

l. J. KARA SSIK' BOILER FEED SYSTEM Filed on; 5, 1939 STEAM L 2 STAGE fRESSURl-Z IquflKarassik INVENTOR ATTORNEY Patented Dec. 17, 1940 UNITED STATES PATENT OFFICE BOILER FEED SYSTEM Igor J. Karassik, New York, N. -Y., assignor to Worthington Pump and Machinery Corporation, Harrison, N. 1., a corporation of Delaware Application October 3, 1939, Serial No. 297,650

4 Claims.

. This invention relates to boiler feed pumps and l5 termediate pressures as specified, such as the boiler feed cycle wherein the feedwater is vdeaeratecl in an open or direct contact type heater and taken therefrom by the boiler feed pump at a temperature of approximately 212 F, and has its pressure :0 raised in the 'pump to from 800 to 1100 lbs. per

sq. in. and discharged by the pump through one,

or more closed or surface type feedwater heaters, where its temp'erature'is raised to approximately 350 F. Fromthe closed type heater it passes to the economizer and boiler.

Such a system has the advantage of a relatively simple construction of boiler feed pump in as much as the stufi'ing boxes of the pump are submitted neither to high pressures nor to high temperatures, but it requires closed or surface type feedwater heaters, which must be designed to accommodate the full discharge pressure of the pump. Such requirements for heaters result in high initial cost of the heaters as well as relatively high maintenance cost and the inconvenience of maintaining the heaters.

To obviate the disadvantages presented by the above system, as well as for various other considerations in power plant heat balance, a system has been utilized of late years wherein a booster pump Lflis employed for receiving the feedwater from the deaerating. feedwater heater or other suitable source The booster pump discharges the feed- ;water into and through one or more closed or '.surface type feedwater heaters at pressures of approximately 250 to 350 lbs. per sq. in. v The temperature of the feedwater is raised in'thefinal heater to approximately 350 F. and is taken therefrom by the boiler feed pump, which discharges it under its final pressure into the economizer and thence to the boiler; This type of boiler feed system eliminates the use of closed or surface type feedwater heaters designed for handling water at high pressures with a resultant decrease in initial cost and maintenance cost, but puts an added burden upon the boilerfeed pump in that it must be designed to handle the feed-. water under high suction pressure and high temperature, These conditions make necessary complicated and expensive stuffing boxes and packing with pressure break-down and leak-off features, resulting in acomplicated, relativelyexpensive pump structure.

An object of the present invention is the provision of a boiler feedwater system and pump which combine the advantageous features of both the systems above referred to, while eliminating their undesirable features. More specifically, the present invention comprises the employment of a multi-stage centrifugal boiler feed pump having its stage impellers arranged so that the end thrust of the pump is balanced without resort to balance structures, and with the lowest pressure stages at the ends of the pump, whereby the stufiing boxes will be subjected only to the lowest pressures in the pump. It further embraces the connection or interposition of a closed or surface type feedwater heater or heaters between intermediate stages of the pump, thereby eliminating the necessity of designing the feedwater heater or heaters to withstand the full discharge pressure of the pump, of designing the stufiing boxes and packing of the pump to withstand either the full final discharge temperature of the feedwater 'or the-high pressure corresponding thereto, and also otherwise'materially reducing the cost'of a boiler feed system by precluding the use of booster pumps, etc.

Another object of the present invention is to provide in a boiler feed system a boiler feed pump embodying characteristics whereby the drips or condensate from the closed or surface type feedwater heaters may be delivered to the feedwater line by induction into the boiler feed pump at one of its intermediate stages.

Withthese and other objects in view, as may appear from the accompanying specification, the invention consistsof various features of construction and combination of parts which will be first described in connection with the accompanying drawing showing diagrammatically a boiler feed system constructed in accordance with the present invention, showing the boiler feed pump in longitudinal section. The features forming the invention will be specifically pointed out in the claims.

Referring more particularly to the drawing, the boiler feed pump I comprises a casing 2 having the various stage suction and discharge passages formed therein and carrying the shaft -3 upon which the various stage impellers are mounted.

The boiler feed pump receives the suction water through thesuction inlet 4 to the first stage 5] The first stage 5, which is the lowest pressure stage in the pump, is located at one end of the casing and discharges into its volute 6 and the connecting passage I into the intake 8 of the second stage impeller 9. The second stage impeller 9, which is the second lowest pressure stage of the pump,

where, it passes through suitable piping l8 to the suction IQ of the third impeller of the boiler ter-balancing together feed pump. Steam passes transversally through the shell l6 of the heater, across the tubes 15, from the steam coil 2|. The feedwater, after passing through the feedwater heater M to the third stage impeller 20, is then successively passed through the successive stages ofthe pump, being finally discharged from the last or highest pressure stage impeller through the discharge 23 to the boiler or economizer. The various stages of the pump other than the stages connected to the feedwater heater l4 have their discharges con- 1 nected to the suction of the successive stages through suitable passages or pipe conduits 24. While in the drawing the second and third stages of the boiler feed pump are shown as connected to the feedwater heater, or, in other words, while the feedwater heater I4 is shown interposed between the second and third stages of the pump, it may be interposed between any two successive intermediate stages of thepump, such as the third and fourth stages,.etc., without departing from the spirit of the present invention.

By particular reference to the drawing it will be noted that the various stage impellers of the pump are arranged in opposing sets for the purpose; of counter-balancing and overcoming end thrusts in the pump and eliminating the need of counter-balancing structures.

Such a pump, that is, a pump inherently embodying in its construction the end thrust counwith the placing of the lowest pressure stages at the ends of the pump, is vital in the successful and practical arrangement of the present boiler feedwater system, in that it readily permits the interposing of the high mat stage feedwater heater between successive stages of the pump 50 that the stuffing boxes of the pump will not be subjected to the high temperatures of the final discharge boiler feedwater and also the connecting of the feedwater heater between the intermediate stages of the pump will not interfere with the end thrust balancing-action of the pump. I

This type of boiler feed pump further permits the induction of the drips or condensate from the feedwater heater l4 into the boiler feed line by its induction into an intermediate stage of the pump. In the drawing the condensate is shown as taken from the hot well 25 of the feedwater heater Is by a booster pump 26 of any approved construction. The discharge 2'! of the booster pump 26 is connected by suitable piping 28 to one of the interstage connection conduits of the boiler feed pump 1 so that the condensate is delivered to the suction of an intermediate stage impeller of the boiler feed pump at a pressure equal to or greater than the suction pressure of such stage. The condensate thus merges with the boiler feedwater and passes into the system without upset- IS in the shell ting the balance of the pump or interfering with its efi'iciency.

Another feature of the pump of the present application which makes it particularly applicable to the reintroduction of the feedwater thereinto is the fact that the maximum pressure across any two adjoining chambers in the pump is that of one stage.

It will be understood that the invention is not to be'limited-to the specific construction or arrangement of parts shown, but that they may be widely modified within the invention defined by the claims.

' What is claimed is:

1. In a feedwater system for boilers, in combination, a multi-stage centrifugal boiler feed pump having its two lowest pressure stage impellers at its opposite ends, a closed surface type feedwater heater, one of the intermediate stages of said pump having its discharge connected to the inlet of said heater, the outlet of said heater being connected to the suction of a successive stage of said pump, and means to deliver the condensate from said heater to said pump at one of the intermediate stages of the pump.

2. In a feedwater system for boilers, in combination, a multi-,stage centrifugal boiler feed pump having its two lowest pressure stage impellers at its opposite ends, a closed surface type feedwater heater, one of the intermediate stages of said pump having its discharge connected to the inlet of said heater, the outlet of said heater being con nected to the suction of a successive stage of said pump, a booster pump for withdrawing the condensate from said heater and having its discharge connected to the suction of an intermediate stage of the boiler feed pump for introducing the condensate into the boiler feedwater passing through the boiler feed pump.

3. In a feedwater system for boilers, in combination, a multi-stage centrifugal boiler feed pump having the two lowest pressure stage impellers at its opposite ends, a closed surface type feedwater heater, one of the intermediate stages of said pump having its discharge connected to the inlet of the heater, the outlet of said heater being connected to the suction of the next successive stage of the pump to the stage which has its discharge connected to the heater inlet, and means to deliver the condensate from said heater into an intermediate stage of the pump at a pressure in excess of the pressure in the pump at the point of introduction of the condensate into the pump.

4. In a feedwater system for boilers, in combination, a multi-stage centrifugal boiler feed pump having stufiing boxes and including a plurality of stage impellers arranged in back to back sets to compensate for end thrust and having th two 7 lowest pressure stage impellers at the opposite ends of the pump whereby the stufling boxes will be subjectedto'the lowest pressure stages in the pump, a feedwater heater, one of the intermediate stages of said pump having its discharge connected. to the inlet of said heater the outlet of said heater being connected to the suction of a successive stage of said pump, a booster pump for withdrawing the condensate from the heater and having its discharge connected to the suction of an intermediate stage of the boiler feed pump for introducing thecondensate into the boiler feedwater.

IGOR J. KARASSIK. 

